S&S Cycle Conversion Kits — 1986-2021 Harley-Davidson Sportster Models

S&S Cycle 1250cc conversion kit for 1986-2021 Harley-Davidson Sportster models, increasing displacement from 883cc or 1200cc without requiring machine work or piston rebalancing. Kit includes forged 5cc pop-up pistons, S&S 3-9/16" bore cylinders, and all gaskets needed for assembly.

Features

• Forged 5cc pop-up pistons with coated skirts
• S&S 3-9/16" bore cylinders
• Complete gasket set included (MLS head, base, exhaust)
• No machining or rebalancing required
• Assembly lube and instructions included

Specifications

• Brand: S&S Cycle
• Manufacturer Part #: 910-0690
• Displacement Increase: 883cc or 1200cc to 1250cc
• Piston Bore: 3-9/16"
• Weight: 22.15 lb
• Category: Engine Components / Piston Sets

Fitment

Fits 1986-2021 Harley-Davidson Sportster models with 883cc or 1200cc engines. 883 cylinder heads are not compatible with this kit.

Frequently Asked Questions

Will this kit fit my 883 Sportster?

Yes, but you must use a 1200 or newer cylinder head. Original 883 heads are not compatible with this conversion.

Do I need to have the cylinders bored or pistons rebalanced?

No. This kit is pre-machined and balanced — no additional machine work is required.

What's included in the box?

Forged pistons, S&S cylinders, MLS head gasket, base gaskets, exhaust gaskets, assembly lube, and detailed instructions.

Will this increase my horsepower?

The displacement bump adds some power, but S&S recommends pairing it with CNC head porting, performance cams, and exhaust/intake upgrades for best results.

Is this a bolt-on upgrade?

It requires engine disassembly and reassembly. Professional installation is strongly recommended.